These test vectors are extracted from
https://github.com/BLAKE2/BLAKE2/blob/master/testvectors/blake2-kat.json

All json objects that contain '"hash": "blake2b"' have been extracted and
saved in blake2b_test_vectors.json.

Using the blake2b.awk program on blake2b_test_vectors.json, we can
generate v code that can initialize an array of TestVector structures.

awk -f blake2b.awk blake2b_test_vectors.json >test_vectors.v

Copy the contents of test_vectors.v into ../blake2b_test.v
